1. It is not Absolute Sound, but Robert Harley, from whom I bought his first audiophile book back in 1994. A foundation you may have missed.

2. I keep the TONE of the sourced material through the Inspire LP-27's PRE outs going directly to my SUB. There is no filtering in that signal. This blends perfectly with the amp's high-passed full range signal which itself preserves that TONE at those higher frequencies.

3. The nominal low-end spec in the mains is usually the lowest frequency from an actual roll-off that starts much earlier, so you are already missing much of the assumed 50Hz-up from your mains as it is.

4. I was very surprised to hear my amp develop such dynamics and finesse, as I had never heard it do that before the filtering thing, in spite of its great sound out of the box.

5. I assume your position would also preclude you from replacing CAPS, or the like, not to "affect" the original setup. I bet you also believe 1's and 0's are always the same ... Give me a break!

BTW, you keep arguing about the length of cables. I don't understand the relevance of that known fact in the context of the filtering setup I propose. The length of those filters is about a couple inches and these go at the end of existing RCA interconnects feeding the amp. The length of bass cables have nothing to do with this approach.

Finally, there are more sophisticated ways to filter low frequencies in support of better dynamics, headroom and the like in a flea-powered amp-based system which otherwise excels in low-to mid and high frequencies. The proposed simple, inexpensive and apparently non-intrusive filters are a very easy and affordable way of testing your preconceptions.